414 - Significant Decreased Radiation Exposure in Percutaneous Adult Degener...

General Session: MIS-1

Presented by: A. Cannestra - View Audio/Video Presentation (Members Only)


A. Cannestra(1,2)

(1) University of Hawaii, John A Burns School of Medicine, Deparment of Surgery, Honolulu, HI, United States
(2) Lyerly Neurosurgery, Jacksonville, FL, United States


Introduction: Robot-assisted placement of pedicle screws has become increasingly popular in minimally invasive lumbar surgery (MIS). Stimulated EMG measurements are often performed as a verification of pedicle screw integrity in MIS. When using robotics, stimulated EMG is performed after tapping. However, if the cannulation of the pedicle is medial or inferior during the drilling step, tapping may result in a pedicle breach. Additionally, if a breach is present during the drilling step, tapping may extend and worsen it further. Performing an EMG prior to tapping is therefore advantageous for patient safety and construct integrity. Aims and

Objectives: The objective of this study was to evaluate an insulated pedicle cannula for stimulated EMG use during robot-assisted pedicle screw placement. Measurements were compared before and after tapping and across monitoring platforms.

Methods: Adult patients presenting with degenerative lumbar spine disease and scoliosis underwent fusion surgery with fixation using robot-assistance (Renaissance, Mazor Robotics Ltd, Caesarea, Israel) and an insulated cannula. The custom insulated cannula was designed with a 3 cm conductive distal tip corresponding to the depth of drilling into the pedicle. Intraoperative stimulation EMG thresholds were measured prior to and after tapping (4.5mm tap). Measurements were taken using two separate systems, in-house neural monitoring and NVM5 (Nuvasive Corp., San Diego, CA).

Results: A total of 68 pedicles which were cannulated in a percutaneous approach. No breaches were identified by stimulation criteria (all stimulation EMG thresholds were greater than 10mA in all groups). The difference (absolute value) between the cannula and tap was 5.3 +/- 0.3 mA. The tap had equal or lower thresholds 75% of the time (relative to the insulated cannula) and higher values in 25% of the stimulations. When comparing between the two monitoring techniques, the variability was consistent, 3.8 +/- 0.3mA

Conclusions: This is a first report of a new, insulated cannula used in percutaneous robot-assisted pedicle instrumentation. The insulated cannula provided accurate and reliable measures of stimulated EMG thresholds. These measurements were consistent with subsequent tapping with minor variations. Comparison of measurements between the two monitoring systems demonstrated consistent results with only slight variation.